1. Field of the Invention
The present invention relates to an image sensing apparatus and imaging system.
2. Description of the Related Art
There has conventionally been proposed an image sensing apparatus having a pixel array (see Japanese Patent Laid-Open No. 2001-045383). According to the technique disclosed in Japanese Patent Laid-Open No. 2001-045383, a shift register for scanning the respective rows or columns of the pixel array is formed from a plurality of circuit blocks. A decoder circuit for selecting one of the circuit blocks is arranged on the preceding stage of the shift register. By selecting a circuit block by the decoder circuit, scanning of pixels can start for each pixel block including a plurality of pixels in the pixel array.
Recently, image sensing apparatuses such as a video camera and still camera require a high-precision electronic anti-shock (camera shake correction) function. As a technique for implementing the electronic anti-shock function, the present inventor has examined to shift a readout region, which is a partial region of the pixel array, in the direction of camera shake in the pixel array. To shift the readout region in the pixel array in order to implement the electronic anti-shock function, the readout start position of the readout region is changed for each pixel (for each row and each column) in the pixel array.
To change the readout start position of the readout region for each pixel, it is necessary to generate a control signal in a horizontal scanning period for scanning a column of the pixel array. For this purpose, a control signal which changes at a predetermined timing needs to be generated by operating a counter for counting clocks in the horizontal scanning period.
In this case, if the counter, pixel array, and peripheral circuit are formed on a single chip, that is, on a single semiconductor substrate, noise generated upon a change of the counted value of the counter may be mixed in a pixel signal output from the pixel array to a subsequent stage via the peripheral circuit. In particular, the level of noise generated upon a change of the counted value of the counter is different between a pixel signal output at the timing when the counted value is carried, and a pixel signal output at another timing. As a result, a vertical streak of fixed-pattern noise is mixed in an obtained image.